This is the 962nd most frequent Italian word.
sottolineare
To underline or emphasize.
Here 'sottolineare' is used to emphasize or stress something important.
Vorrei sottolineare l'importanza di fare pratica regolarmente.
I would like to underline the importance of practicing regularly.
In this case, 'sottolineare' refers to the action of literally underlining text in writing.
Questa frase è stata sottolineata nel testo per evidenziarne il significato.
This sentence was underlined in the text to highlight its meaning.
Here 'sottolineare' means to highlight or stress important aspects verbally or in discussion.